The Muscles of Mastication
1.20.16 in General
Movement of any of our bones at a joint, is facilitated by groups of muscles. One “set” of muscles allows movement in one direction, for instance, opening of the mouth; while another “set” of muscles causes movement in the opposite direction(closing the mouth) These 2 groups of opposing muscle can not both function at the same time, or we have a dilemma!
And so, a balance or harmony must exist in order for our bodies to function properly. To open our mouths, we rely on some muscles to “pull” the mandible down and back. Muscles such as the Digastric muscles, and the stylohyoid muscles. Gravity also plays a role in opening the mouth.
In contrast, in order to close the mouth, some muscles must overcome gravity and move the mandible in an upward direction. There are 5 pair of muscles which accomplish this:
The external masseters, the internal masseters, the medial pterygoid muscles, the lateral pterygoid muscles and the temporalis muscles. Let me make this easy to picture.
Move your lower jaw upward until it stops. It will most like stop moving upward because your lower teeth hit against your upper teeth, but it was these 5 sets of muscles that caused the upward movement. Put your hands on the sides of your face, and while clenching your teeth together, feel the muscles tighten. The right and left “gum-chewing” muscles can be felt running from your cheek bones to the bottom edge of your lower jaw. If you place your fingers on both “temples” and clench, you can feel the temporalis muscles. These are large fan-shaped muscles on the side of the head, that have fibers running to behind the eyes, and to the tip of the lower jaw. Thus, they help the jaw close. When this set of muscles overwork, we perceive headaches and what feels like pain from our sinus areas. Many times, it is actually muscle pain. You can feel and often see them bulge as we try to close our mouths. These are the muscles of mastication, and of all the forces on our bones, and joints, and teeth, muscles are the strongest and always dominate. It is when these muscles work too much that we cause damage to the rest of the system. But that’s another blog.
Stay tuned in, and keep smiling! Dr. W.